I have also tried Mvelopes in the past, and my experiences match yours.
I currently use the desktop version of YNAB:You Need a Budget (YNAB 4), and I like it much better. Where we failed after a while with Mvelopes, we are succeeding with YNAB, and have been now for the last 3.5 years.
I don't want this to sound like a commercial for YNAB (I will give important caveats about YNAB later), but here is why I believe we have done better now with YNAB than before with Mvelopes. I hope that these reasons will be useful to you when you are evaluating your next options.
As you said, we also found Mvelopes' interface to be slow and glitchy. YNAB 4 is a desktop app (with synching capabilities) that we found to be much quicker and easier to work with than Mvelopes' Flash-based interface. (That was 4 years ago; hopefully Mvelopes has redone their interface since then.)
We also struggled with Mvelopes' connection with our banks. With YNAB 4, there is no connection to the bank: everything has to be entered manually. I initially thought this might be worse, but for us it has been better. I can either enter transactions as they happen on the mobile app, or I can hold on to receipts and enter them every day or two in the evening, categorizing as I go. We always have an up-to-date picture of our finances, and we don't have to mess with trying to match up downloaded transactions that have been screwed up, duplicated, or are missing.
We aren't really using YNAB much differently than we were using Mvelopes, but we have learned a few tricks that I think have contributed to our success. One of the things we do differently is that I don't obsess about the cash accounts too much. Cash accounts, for us, are the hardest to keep track of, because most of our cash transactions don't have a receipt: we are paying a friend or family member for something, or leaving a tip, or something like that which we forget about when it comes time to enter into the software. As a result, the cash account balances get off. I periodically enter a correcting transaction to get the balances right, and have a budget category specifically for this that we have to put money in for these unknown transactions. Fortunately for us, our cash spending is a small percent of our total spending (we usually pay with a credit card) so this bit of untracked spending isn't that big of a concern.
With YNAB, the current month's budget is right in front of you as soon as you open up the app, which makes it easy to adjust your budget during the month, if necessary. With Mvelopes (at least how their app worked 4 years ago), the budget was somewhat hidden after you funded your budget categories, and it was a bit of a pain to move money around between categories. The ability to adjust your budget in the middle of the month is crucial; if you don't do that, you'll get frustrated the first time you find that you don't have enough money in a category for something you need. YNAB makes it very easy to move money around inside your budget.
That having been said, you need to be aware that the current version of YNAB is not a desktop application but a web-based app. YNAB 4, the old desktop version which we have been using, is officially unsupported as of the end of 2016, and I see that it is no longer available for sale. However, if you can somehow obtain it, the YNAB4 help site is still up, and the mobile app you would need to work with it on your phone (called YNAB Classic) is still in the app store.
As I said, the current YNAB is now a web app, complete with automatic downloading of transactions from your bank. I have no experience with it (other than playing around with it a little), and so I can't tell you how quick the interface is or how well the auto-downloading of transactions works.
As an alternative, another web-based solution is EveryDollar, from Dave Ramsey's company. (I have never tried it.) The advantage of this one is that it is free if you choose not to link it to your banks; the automatic downloading of transactions is a paid feature.
I wrote an answer a couple of years ago in which I describe two different approaches that budgeting software packages tend to take. I'm not familiar with Buxfer, so I don't know which approach it takes, but perhaps that answer will help you evaluate all of your software options.
On the behavior side of things, besides the relaxing of the cash accounting I mentioned above, we also involve my wife a little less in the budgeting process than we used to. (This is by her choice!) I am the one who enters all the transactions into the software (she hands me all her receipts), I reconcile the accounts at the end of the month, and I set the budget for the next month. We have been doing this long enough now that she knows what the budget is, and we only need to discuss it if we want to do something different with the budget than we have been doing in the past. She has the YNAB app on her phone and can see where we are at with all of our budget categories.